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Complex Crystal Structures (complex + crystal_structure)
Selected AbstractsThe human ACC2 CT-domain C-terminus is required for full functionality and has a novel twistACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2009Kevin P. Madauss Inhibition of acetyl-CoA carboxylase (ACC) may prevent lipid-induced insulin resistance and type 2 diabetes, making the enzyme an attractive pharmaceutical target. Although the enzyme is highly conserved amongst animals, only the yeast enzyme structure is available for rational drug design. The use of biophysical assays has permitted the identification of a specific C-terminal truncation of the 826-residue human ACC2 carboxyl transferase (CT) domain that is both functionally competent to bind inhibitors and crystallizes in their presence. This C-terminal truncation led to the determination of the human ACC2 CT domain,CP-640186 complex crystal structure, which revealed distinctions from the yeast-enzyme complex. The human ACC2 CT-domain C-terminus is comprised of three intertwined ,-helices that extend outwards from the enzyme on the opposite side to the ligand-binding site. Differences in the observed inhibitor conformation between the yeast and human structures are caused by differing residues in the binding pocket. [source] Cover Picture: Sequential Nucleation and Growth of Complex Nanostructured Films (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 3 2006Mater. Abstract A sequential nucleation and growth process has been developed to construct complex nanostructured films step-by-step from aqueous solutions, as reported by Liu, Voigt, and co-workers on p.,335. This method can be applied to a wide range of materials, and can be combined with top,down techniques to create spatially resolved micropatterns. The cover figure shows images of oriented nanowires, nanoneedles, nanotubes, nanoplates and stacked columns, wagon-wheels, hierarchical films based on wagon-wheels, hierarchically ordered mesophase silicate, and micropatterned flower-like structures. Nanostructured films with controlled architectures are desirable for many applications in optics, electronics, biology, medicine, and energy/chemical conversions. Low-temperature, aqueous chemical routes have been widely investigated for the synthesis of continuous films, and arrays of oriented nanorods and nanotubes. More recently, aqueous-phase routes have been used to produce films composed of more complex crystal structures. In this paper, we discuss recent progress in the synthesis of complex nanostructures through sequential nucleation and growth processes. We first review the use of multistage, seeded-growth methods to synthesize a wide range of nanostructures, including oriented nanowires, nanotubes, and nanoneedles, as well as laminated films, columns, and multilayer heterostructures. We then describe more recent work on the application of sequential nucleation and growth to the systematic assembly of large arrays of hierarchical, complex, oriented, and ordered crystal architectures. The multistage aqueous chemical route is shown to be applicable to several technologically important materials, and therefore may play a key role in advancing complex nanomaterials into applications. [source] Solving crystal structures in P1: an automated procedure for finding an allowed origin in the correct space groupJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2000Maria Cristina Burla Crystal structure solution in P1 may be particularly suitable for complex crystal structures crystallizing in other space groups. However, additional efforts and human intervention are often necessary to locate correctly the structural model so obtained with respect to an allowed origin of the actual space group. An automatic procedure is described which is able to perform such a task, allowing the routine passage to the correct space group and the subsequent structure refinement. Some tests are presented proving the effectiveness of the procedure. [source] EXAFS study of local atomic order about iodine in thyroxine, rat, human and sheep thyroidsJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2008B. R. Orton Radioactive 125I emits short-range Auger electrons and represents a human health risk when incorporated in thyroglobulin of the thyroid. Quantitative evaluation of this risk can only be realised if local atomic order about iodine in the thyroid is known. Here, extended X-ray absorption fine structure (EXAFS) has been used to probe the local structure about iodine in pure thyroid hormone, thyroxine. These data are consistent with a model where iodine is bound to a single iodinated carbon ring linked to an oxygen atom, similar to a previously published model for monoiodotyrosine, a major iodinated residue in thyroglobulin. Several structural models for the local environment of iodine from rat, human and sheep have been tested and these data are found to be compatible with a slightly modified environment with respect to that found for thyroxine. The best-fit models include the following three components: (i) iodine covalently bonded to a tyrosine ring, as found for thyroxine; (ii) iodine bonded quasi-covalently to a carbonyl ligand in partially filled (50%) sites; (iii) partially filled sites (50,40%) of carbonyl ligands, with oxygen at van der Waals distances from iodine. Advantages of using Fourier-filtered EXAFS for complex crystal structures are discussed. [source] Structures from powders and poor-quality single crystals at high pressureJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2005Malcolm I. McMahon The use of single-crystal techniques and quasi-single-crystal samples in solving and refining complex crystal structures at high pressure is reviewed. In particular, recent studies of the incommensurate and modulated structures found in a number of elemental metals at high pressure are focused on. [source] New opportunities in biological and chemical crystallographyJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2002John R. Helliwell Banerjee [Proc. R. Soc. (1933), 141, 188,193] offered a new way of approaching the crystallographic phase problem which not only broke new ground beyond the `trial and error' structure solution method of that time but also heralded the extremely powerful direct methods of crystallography of the modern era from the 1970s onwards in chemical crystallography. Some 200000 crystal structures are known today. More complex crystal structures such as proteins required new experimental and theoretical methods to solve the phase problem. These are still evolving, and new methods and results involving synchrotron radiation at softer X-ray wavelengths (2,Å) are reported. In addition, an overview is given of the new opportunities that are possible for biological and chemical crystallography, especially via harnessing synchrotron radiation and neutron beams. [source] Metal-free MIRAS phasing: structure of apo-S100A3ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2002Peer R. E. Mittl S100 proteins are involved in metal-dependent intracellular signalling. Metal-free S100A3, a cysteine-rich Ca2+ - and Zn2+ -binding protein, has been crystallized by vapour diffusion under the strict exclusion of oxygen and in the absence of divalent metal ions. Metal binding induces large conformational changes, rendering the apo-S100A3 crystals very sensitive to various metal compounds. Therefore, the structure was solved by MIRAS phasing using potassium iodide and xenon derivatives. Iodide replaces a water molecule at the surface of the S100A3 protein, whereas xenon binds in a hydrophobic cavity at the dimer interface. Despite significant non-isomorphism, the combination of both derivatives was sufficient for structure determination. The overall apo-S100A3 structure resembles the structures of metal-free S100B and S100A6 solution structures. In contrast to the NMR structures, the EF-hand loops are well ordered in the apo-S100A3 crystal structure. In the N-terminal pseudo-EF-hand loop a water molecule occupies the position of the Ca2+ ion. The C-terminal canonical EF-hand loop shows an extended conformation and a different helix arrangement to other S100/metal complex crystal structures. [source] Three-Dimensional Protein,Ligand Interaction Scaling of Two-Dimensional FingerprintsCHEMICAL BIOLOGY & DRUG DESIGN, Issue 5 2009Lu Tan We introduce a computational scaling methodology that utilizes protein,ligand interaction information extracted from complex crystal structures to enrich similarity searching using structural fingerprints with compound class-specific information. Scaling factors are derived to emphasize fingerprint bit positions that result from interacting fragments of bound ligands and correspond to frequently occurring structural features. Through interaction-based scaling, this information is transferred to standard fingerprints of multiple reference compounds. In systematic search calculations, fingerprints scaled on the basis of three-dimensional information are found to produce higher recall rates of active compounds than alternative types of scaled and non-scaled fingerprints. [source] Vibrational spectroscopic analysis of 3-hydroxy-1,5-diazacyclooctane and its copper(II) complexJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2001Lian He The changes in the vibrational spectra between 3-hydroxy-1,5-diazacyclooctane and its copper(II) complex were studied by Fourier transform Raman and infrared spectroscopy for the first time. The vibrational bands near 472 and 204 cm,1 were assigned to the Cu,N and Cu,O stretching vibrations in the copper(II) complex, respectively. CNDO/2M and AM1 methods were used to calculate Mulliken orders and bond distances on the basis of the copper(II) complex's crystal structure. The mechanism of the changes in the vibrational spectra is discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||